Conventional web-based systems permitting the storage and display of digital videos typically only allow commenting on the video as a whole. In particular, if viewers wish to comment on or otherwise reference a particular portion of the video, they are obliged to explicitly describe the portion by text or time in the video and other indirect means. Conventional systems also have simplistic controls for annotating a video, to the extent that they allow such annotation at all. Rather, such systems either allow only the owner (e.g., a user who uploaded the video) to add annotations, or else allow all users to do so, without restrictions.